domingo, 6 de enero de 2013

Milky Way's Core Source of Monster Energy Outflows

"Monster" outflows of charged particles from
the center of our Galaxy, stretching more than halfway across the sky,
have been detected and mapped with Australia's CSIRO's 64-m Parkes radio telescope.
The outflows were were detected by astronomers from Australia, the USA,
Italy and The Netherlands. They report their finding in today's issue
of Nature.

"These outflows contain an extraordinary amount of energy — about a
million times the energy of an exploding star,"
Dr Ettore Carretti. But the outflows pose no danger to Earth or the
Solar System. The speed of the outflow is supersonic, about 1000
kilometres a second. "That's fast, even for astronomers," Dr Carretti
said. "They are not coming in our direction, but go up and down from the
Galactic Plane. We are 30,000 light-years away from the Galactic Centre, in the Plane. They are no danger to us."

From top to bottom the outflows extend 50,000 light-years [five
hundred thousand million million kilometres] out of the Galactic Plane.
That's equal to half the diameter of our Galaxy (which is 100,000
light-years — a million million million kilometres — across). Seen from
Earth, the outflows stretch about two-thirds across the sky from horizon
to horizon.

The outflows correspond to a "haze" of microwave emission previously
spotted by the WMAP and Planck space telescopes and regions of gamma-ray
emission detected with NASA's Fermi space telescope
in 2010, which were dubbed the "Fermi Bubbles". The WMAP, Planck and
Fermi observations did not provide enough evidence to indicate
definitively the source of the radiation they detected, but the new
Parkes observations do.

"The options were a quasar-like outburst from the black hole at the
Galactic Centre, or star-power — the hot winds from young stars, and
exploding stars," said team member Dr Gianni Bernardi of the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Massachusetts. "Our observations tell us it's star-power."

In fact, the outflows appear to have been driven by many generations
of stars forming and exploding in the Galactic Center over the last
hundred million years.
The key to determining this was to measure the outflows' magnetic
fields.

The new observations also help to answer one of astronomers' big
questions about our Galaxy: how it generates and maintains its magnetic
field.
"The outflow from the Galactic Centre is carrying off not just gas and
high-energy electrons, but also strong magnetic fields," said team
member Dr Marijke Haverkorn of Radboud University Nijmegen in The Netherlands. "We suspect this must play a big part in generating the Galaxy's overall magnetic field."